Differential expression of lymphokines by CD4+ T cells plays a key role in proper modulation of the immune response. Consequently, aberrant control of lymphokine expression can have wide ranging impact on the progression of many infectious diseases such as tuberculosis and HIV as well as autoimmune diseases such as diabetes and multiple sclerosis. Th1 cells, which secrete IFN-gamma, IL-2 and lymphotoxin, direct delayed type hypersensitivity responses and are important in defense against intracellular organisms. Th2 cells, which produce IL-4, direct allergic or anti-inflammatory responses and protect against helminth infections. Regulation of IFN-gamma, IL-2 and IL-4 occurs primarily at the level of gene transcription, but the basis for the selective expression of these lymphokines by the various T cell subsets remains unclear. The overall objectives of this proposal are to define the molecular mechanisms by which IFN-gamma and IL-4 are differentially regulated by Th1 and Th2 CD4+ T cells and to develop an animal model in which the biological importance of developing the polarized population of T cells in response to infection and autoimmune disease can be assessed. Our recent studies have defined a key regulatory element in the IFN-gamma promoter which may contribute to the selective expression of IFN-gamma in Th1 cells and lack of expression in Th2 cells via interaction with factors which can mediate and repress expression and by methylation. The goal of this proposal is to use a two pronged approach to test this hypothesis. The first approach will utilize transient transfection of constructs containing this element into Th1 and Th2 cells to dissect the molecular pathway involved. The second concomitant approach will utilize in vivo promoter swapping experiments designed to determine the physiological importance of this element in the context of the endogenous gene and to address the role of methylation. These studies will build upon the candidate's previous training and allow her to gain significant new expertise in the generation and assessment of transgenic animals and in analysis of the complexity of the immune response in a whole animal context. These skills are essential for her development into an independent investigator. The sponsor's laboratory provides an ideal environment in which to pursue the proposed experiments since mouse embryo manipulation has been successfully utilized by this group and others at this institution and all the tools necessary to analyze the mice are available.